Armada, it feels like a task for me to watch one whole episode
Energon I quite enjoyed until about half way in, then it just got dull
And I find Cybertron is actually not too bad once you get past the god awful theme tune

Armada with the animation flaws was at least pretty neat and I liked the new characters... Energon was too much. Kicker is the worst thing ever and how he was violated by primus ruined the whole series for me.

There is a reason they skipped to cybertron DVD release and ignored energon.

It's a three-way tie between Armada, Energon, and Cybertron. All three showed a lot of promise at the beginning but quickly became insanely boring. Armada, particularly, could have been a great series with the return of Unicron but that was completely botched IMO.

I haven't seen a complete series since BM...seen most of RiD, a little over half of Armada and one or two episodes each of Energon and Cybertron...Honestly it's a four way tie between all of them. I just couldn't stand the very few eps I saw of Energon and Cybertron, the damn kids ruined every single thing about Armada, and the writing and voice acting in RiD makes me roll my eyes. I know their all dubs, but god...damn.

Headmasters: killing Optimus Prime for the second time and the terrrible ending scene for Rodimus Prime. For me far worse than anything that RID/AEC could offfer up poorly. BM is a close second to my worst.